As the design evolved, conductive covers were specified in order to shield them from RFI. Nickel was selected for a very important reason.
What does this have to do with audio connectors, and why is nickel as poor of a choice for audio connectors as it is a good one for pickup covers?
The Gibson team discovered that nickel's poor electrical conductivity (compared with other alloys) induced lower eddy current levels. These lower levels resulted in a more transparent sound when compared with pickups with covers made from more conductive metals.
For the very same reason nickel works for guitar pickups, it is a poor choice for audio connectors.
You will find a nickel substrate in many popular connectors. Manufactures use it to simplify the plating process (for cosmetics) and not for its sonic properties.
So, when you buy one of our cables, know that ETI's connectors have only two layers - the tellurium copper base layer and the surface plating (either gold or rhodium).
You can read more about the connectors we specify in this link.